1. Field of the Invention
The present invention relates to a method for etching iron and iron alloy materials and an etchant for use therein. More particularly, the method and etchant of the present invention aggressively etch an iron material previously wound and bonded with epoxy cement without destroying any existing epoxy bond in the material.
2. Description of Prior Art
Metallic materials are exposed to etching treatments for a variety of purposes. For example, a metallic material such as aluminum may be subjected to an etching treatment before it is bonded to a fluorocarbon resin. U.S. Pat. No. 3,115,419 to Dale illustrates such a method wherein aluminum materials are subjected to an etching treatment using an etchant comprising an aqueous solution of either acetic acid, sodium chloride, cupric chloride and water or trichloracetic acid, ferric chloride, chloroplatinic acid and water.
Etchants may also be used as part of a method for producing an electrically conductive pattern. U.S. Pat. No. 4,093,504 to Ponjee et al. illustrates such a method wherein an electrically conductive pattern is formed by forming a uniform layer of indium oxide on an electrically insulating support, applying to said indium oxide layer an etch-resistant coating in the negative image of the desired pattern, and applying to said thus coated layer an aqueous hydrochloric acid etching solution containing in addition to the acid, ferric chloride in a quantity between 0.01 mol/l and the saturation concentration thereof. U.S. Pat. No. 5,185,059 to Nishida et al. illustrates a similar process wherein an etchant of hydroiodic acid or a hydroiodic acid-ferric chloride aqueous solution mixture is used to leave an indium-tin-oxide electrode pattern.
Still further, metal surfaces may be etched prior to having a coating such as polytetrafluoroethylene applied thereto. U.S. Pat. No. 5,185,057 to Playdon illustrates an etching process wherein a solution containing ferric chloride and phosphoric acid is applied to a metal surface to be coated. During this etching process, an effective concentration of ferric ions is maintained by diffusing an oxidizing agent which is chlorine gas or a compound which forms HOCl in solution through the etching tank.
Generally accepted practice for etching ferrous alloys involves concentrated orthophosphoric acid or concentrated hydrochloric acid. However, many motor parts in use today consist of a wound iron core material bonded with epoxy cement. The use of concentrated orthophosphoric or hydrochloric acid etchants on these parts has resulted in damage to the epoxy cement bonded to the iron materials.
Thus, there is a need for an etchant which yields an iron surface that bonds well to a coating material, such as an epoxy material, but does not destroy the existing epoxy cement or material already bonded to the iron material.